Abstract

Background: Recurrence following endovascular treatment of intracranial aneurysm can be seen in one of four intracranial aneurysms. The recurrence is attributed to either coil compaction or aneurysm growth but these processes have not been studied if these processes are distinct processes or if they act in concert.

Methods: Aneurysm recurrence was identified by an independent review of immediate post-procedure and follow-up angiographic images of consecutive patients who had endovascular treatment of intracranial aneurysms at two medical centers from September 2006-April 2010. The voxel size of the coil mass and aneurysm sac, and the adjacent parent artery were measured using the Analyze Software (Mayo Clinic). To avoid errors associated with absolute measurements on different images, the voxel sizes of the coil masses and aneurysm sac were expressed as a ratio to the voxel sizes of the parent vessel diameter on immediate post-procedure and follow-up angiograms. Increase of aneurysm area or decrease in coil mass of 30% or greater on follow-up angiogram was used to define “aneurysm growth” and “coil compaction”, respectively

Results: Based on our criteria, a total of 29 out of 201 patients had aneurysm recurrence at mean follow of 9.1 months (SD 6.3). Of these, 11 patients had coil compaction and 18 had aneurysm growth. There were no patients with both aneurysm growth and coil compaction. The rate of aneurysm growth and coil compaction among patients who were treated for ruptured intracranial aneurysms was 11% and 7% respectively. There were no events of new aneurysmal rupture in either the 11 patients who had coil compaction or the 18 patients who had aneurysm growth over a mean follow-up period of 22 months (range of 9-42 months). Retreatment was performed in 15 of the 18 patients with aneurysm growth and 8 of the 11 patients with coil compaction. The 1 month stroke and death rate after retreatment was similar between patients with aneurysm recurrence due to coil compaction or aneurysm growth.

Conclusion: Our study suggests that coil compaction and aneurysm regrowth are two distinct processes that can contribute to aneurysm recurrence. Further studies would have to identify whether each mechanism is associated with a differential risk of aneurysmal rupture.